Socket-projection fixing assembly

ABSTRACT

A socket-projection fixing assembly for a horizontal wet joint ( 3 ) between two cylindrical concrete sections ( 2.2 ′) for a wind turbine tower, which comprises socket-projection fixing device with an active internal reinforcement ( 8 ) and a socket-projection fixing device with a passive internal reinforcement ( 7 ) so that said reinforcements each include an embedded portion which is embedded in a first section of said cylindrical sections and a projecting portion which projects from said first section and is housed in a duct ( 9, 10 ) in a second section of said cylindrical sections. Said active internal reinforcement includes tightening means ( 14, 16 ) which are arranged in said projecting portion of said active internal reinforcement and against a supporting surface ( 15 ) of one of said cylindrical sections, and said passive internal reinforcement includes cured material ( 12 ) which is arranged around said projecting portion o said passive internal reinforcement ( 7 ) and adheres to the interior of said duct ( 10 ).

FIELD OF THE INVENTION

The present invention relates to a socket-projection fixing assembly,internally reinforced, for a horizontal wet joint between twocylindrical prefabricated concrete sections for a wind turbine tower, orbetween a cylindrical prefabricated concrete section and a concretefoundation for a wind turbine tower. Although hereinafter reference ismade solely to the horizontal wet joint between two sections for thesake of simplicity, this in any way limits the scope of the invention.

The principal sector of application of the invention is therefore thebuilding sector, particularly concrete structures, in the renewable orgreen power generating industry, specifically wind power.

BACKGROUND TO THE INVENTION

A method is known for erecting wind turbine towers on the basis ofcylindrical sections which are connected to each other coaxially, oneabove the other, thus creating horizontal joints between successivesections. Said cylindrical sections may in turn be pre-formed by curvedelements or voussoirs which are joined side by side, thus creatingvertical joints, until a section is closed.

Said horizontal joints are normally wet joints, i.e. they normallycomprise material which is applied in a liquid or plastic form in thering, and is left to cure until the corresponding successive sectionsare fastened together in a substantially hermetic manner. The ring isthe space in the shape of a circular crown which is located between thetwo facing edges of successive sections.

However, because of the considerable stresses imposed by the enormousdimensions and heavy weights of the sections to be connected, saidhorizontal wet joints are often supplemented by internally reinforced,socket-projection fixing devices, i.e. fixing devices with reinforcementarranged essentially inside said sections and distributed between twosuccessive sections so that it is embedded in the concrete of one ofsaid successive sections and accommodated in a duct of the other of saidsuccessive sections and anchored thereto to secure both sectionstogether. Said internal reinforcement may be a passive reinforcementwhich is simply stretched and anchored to improve to some extent thebehaviour of the joint when said joint is subjected to tension, butwhich increases the length of the erection process because it requires aminimum time for setting of the anchoring mass of a horizontal wet jointbefore forming the next horizontal wet joint; or said internalreinforcement may be an active reinforcement which is anchored andstretched to improve substantially the behaviour of the joint when saidjoint is subjected to tension, but which requires additionalinstallation operations.

In any case, the voussoir or the section having the reinforcementpartially embedded therein (with a portion projecting therefrom) iscalled a male voussoir or male section, and the voussoir or the sectionhaving a space for accommodation in said portion projecting from themale voussoir or the male section is called the female voussoir orfemale section. On the other hand, a voussoir or section having bothreinforcements partially embedded in it and ducts for receivingreinforcements partially embedded in another voussoir or section, iscalled a mixed voussoir or section.

By way of example, document ES 1060629 U discloses sheaths 4 previouslyfastened to the concrete of a lower section, which sheaths 4 receivebars 5 partially embedded in the concrete of an upper section so thatthey have a portion which projects outside said upper section, saidsheaths 4 being filled with mortar. In this manner bars 5(reinforcement) are adhered by means of mortar to sheaths 5 integralwith the concrete. In this case the reinforcement is passive, notstretched, and normally in the form of a corrugated bar which acts oncethe mortar has set.

Alternatively, and also by way of example, document EP 2253782 A1discloses a system of connection between two adjacent prefabricatedsections 2, one of said sections 2 being provided internally with apretensioned cable 4 (reinforcement) partially embedded in the concretewith a portion 4a of cable projecting outside of it and housed in a duct24 provided in the other of said sections 2, which has a face whichincludes an enlargement 21 which leads duct 24 to an outlet throughwhich said portion 4a emerges and is anchored by a stop 22. In this casethe reinforcement is active and is stretched, after its installation, inorder to compress the concrete, and which may be in the form of a bar(or bolt) or cable.

However, it is necessary to provide a horizontal wet joint which, on theone hand, has internal reinforcements for improving the behaviour of thejoint when it is subjected to tension and which, on the other hand,involves the smallest possible number of additional operations andextends to the least possible extent the duration of the erectionprocess.

SUMMARY OF THE INVENTION

The object of the invention is therefore to provide an internallyreinforced, socket-projection fixing assembly for a horizontal wet jointbetween two cylindrical prefabricated sections of concrete for a windturbine tower, which involves the least possible number of additionaloperations and which extends to the least possible extent the durationof the process of erecting said tower.

Specifically the invention relates to an internally reinforced,socket-projection fixing assembly for a horizontal wet joint for a windturbine tower which comprises at least one socket-projection fixingdevice with an active internal reinforcement and at least onesocket-projection fixing device with a passive internal reinforcement sothat said active internal reinforcement and said passive internalreinforcement each include a portion (hereinafter referred to as“embedded portion”) which is embedded in a first section of saidcylindrical prefabricated sections, and a portion (hereinafter referredto as “projecting portion”) which projects from said first section andis housed in a duct in a second section of said cylindricalprefabricated sections, wherein said active internal reinforcementincludes means of tightening which are arranged in said projectingportion of said active internal reinforcement and against a supportingsurface of one of said cylindrical prefabricated sections so that saidactive internal reinforcement is anchored to said supporting surface andstretched by means of said tightening means, and wherein said passiveinternal reinforcement includes cured material which is arranged atleast partially around said projecting portion of said passive internalreinforcement and adhered to the inside of the passive reinforcementduct in which is arranged said projecting portion of said passiveinternal reinforcement.

Of course at least one of said first and second sections may be formedby voussoirs.

Said tightening means may comprise a nut which is threaded onto athreaded end of said active internal reinforcement and which istightened optionally with the insertion of an anchor plate and/or acurable levelling and/or supporting material against said supportingsurface.

A partial pre-tensioning is preferably used in said horizontal wetjoint, i.e. said active internal reinforcement is stretched so that itexerts a force which pre-compresses said horizontal wet joint andprevents the de-compression of said horizontal wet joint for appliedloads below a predetermined load threshold, which is in turn lower thanthe maximum design load. From said load threshold, i.e. for appliedloads higher than said load threshold and up to said maximum operatingload, the de-compression of the joint may takes place and said passiveinternal reinforcement then interacts by resisting the tensions to whichthe joint may be subjected. It enables the pre-tensioning of the jointresulting from the stretching of the active reinforcement(s) to beadapted to the normal or fatigue loads and allows the passivereinforcement(s) to be used for the extreme or breaking loads, bybenefiting from and combining the characteristics and advantages of eachtype of reinforcement.

If said first section and said second section comprise voussoirs, it ispreferred that said socket-projection fixing assembly, internallyreinforced, according to the invention, comprises a number ofsocket-projection fixing devices with active internal reinforcementwhich is at the same time a multiple of the number of voussoirs in thefirst section, a multiple of the number of voussoirs in the secondsection and a divisor of the total number of socket-projection fixingdevices, i.e. by including both socket-projection fixing devices with anactive reinforcement and socket-projection fixing devices with a passivereinforcement. Such an arrangement provides an even distribution of thesocket-projection fixing devices with an active internal reinforcement,and an identical distribution of the socket-projection fixing devices ineach voussoir forming each of said first and second sections.

In the case of a socket-projection fixing device with active internalreinforcement of the socket-projection fixing assembly according to theinvention, and if said tightening means comprise an anchor plate andsaid second section is arranged above said first section, said anchorplate may then comprise one or more bores which may act as venting ductsfor the air outlet during the insertion of curable material in saidactive reinforcement duct or in a sheath arranged inside said activereinforcement duct.

In the case of a socket-projection fixing device with active internalreinforcement of the socket-projection fixing assembly according to theinvention, said second section preferably has a working facing whichincludes a hole in correspondence with the distal end of said projectingportion of said active internal reinforcement, said hole having a depthsuch that it extends at least to said active reinforcement duct incorrespondence with said distal end of said projecting portion of saidactive internal reinforcement, with dimensions such that said tighteningmeans can be housed inside said hole, thus allowing both the applicationof said tightening means to said distal end of said projecting portionof said active internal reinforcement and the anchoring and tensioningof said active internal reinforcement by means of said tightening means.In this case, said supporting surface is located in the inner wall ofsaid hole. Due to the prefabricated nature of said cylindrical sectionsthe geometry of said hole must be such that a suitable release angle isprovided. Moreover, if said tightening means comprise an anchor plate,said supporting surface of said hole is preferably formed with asuitable flatness to allow direct support of the anchor plate on saidsupporting surface without the need for intermediate parts or productssuch as levelling and supporting mortars, and consequently to allow theimmediate at least partial tightening of the tightening means during theinstallation process, although curable materials for said supportingface may of course be used additionally or alternatively.

In the case of a socket-projection fixing device with passive internalreinforcement of the socket-projection fixing assembly according to theinvention, said passive reinforcement duct may include a sheath,possibly corrugated, which receives said projecting portion of saidpassive internal reinforcement, and which is filled with curablematerial (mortar, resin or similar). Moreover, if said second section isarranged above said first section, said passive reinforcement duct mayinclude a sheath, possibly corrugated, which receives said projectingportion of said passive internal reinforcement, and said second sectionmay have a working facing which includes a hole in correspondence withthe distal end of said projecting portion of said passive internalreinforcement, said hole having a depth such that it at least extends tosaid passive reinforcement duct in correspondence with said distal endof said projecting portion of said passive internal reinforcement, andsaid sheath having an extension which extends along said hole until itreaches at least the inlet of said hole. Said sheath may then be filledwith a curable material (mortar, resin or similar) via said filling holeand said extension, which provides the fixing of said passive internalreinforcement in the sheath and anchorage by adhesion of said passiveinternal reinforcement. The ring formed between said cylindricalprefabricated sections may also be filled with a curable material(mortar, resin or similar) via said filling hole and said extension.

Said hole does preferably not open to the facing opposite the workingfacing, and said working facing is preferably the facing orientatedtowards the inner space enclosed by said second section.

The combination of active internal reinforcement and hole provides,during the installation, convenient access to the active reinforcementvia the existing hole. This allows the immediate, simple anchorage ofthe active reinforcement by means of said tightening means in order tominimise its influence on the times for the process of installation ofthe corresponding tower. Moreover, the hole may finally be filled withcurable material (grout material or similar), thereby embedding theentire active internal reinforcement with the tightening means, andproviding reliable, permanent protection basically without anymaintenance of any of the parts, particularly protection againstcorrosion of the metal parts which are normally used in the tighteningmeans of active reinforcements. In this case, said hole is filled withsaid curable material, preferably until a curable material surface isflush with the surface surrounding the prefabricated section in order toeliminate as far as possible any structural discontinuity. Moreover, ifa sheath is provided in said active reinforcement duct for saidprojecting portion of said active reinforcement, said sheath can then befilled with a curable material (mortar, resin or similar).

The combination of active/passive internal reinforcement and hole mayalso make it easier to ensure that the vertical development of saidactive/passive internal reinforcement (and hence the verticaldevelopment of the associated duct) is not parallel with the generatingline of said cylindrical prefabricated sections. It is known that thecylindrical sections for the erection of wind turbine towers may betapered in the ascending direction to provide an essentially conicaltower. In this case, said cylindrical prefabricated sections will begenerated by a generatrix inclined towards the axis of revolution in theascending direction, and to facilitate the insertion of said projectingportion of said active/passive internal reinforcement in saidcorresponding duct during an operation of vertical lowering of one ofsaid cylindrical prefabricated sections onto another section, saidactive/passive internal reinforcement may not be parallel with thegeneratrix, preferably being parallel with the vertical axis ofrevolution. The combination of active/passive internal reinforcement andhole may also make it easier for said active/passive internalreinforcement to be arranged essentially centred in the thickness ofsaid cylindrical prefabricated sections.

Be that as it may, the duct will have a specific geometry depending onthe characteristics of each case. For example, in the case of asocket-projection fixing assembly according to the invention, with anactive reinforcement in the form of a cable, the duct may then have acurved vertical development.

With a socket-projection fixing assembly according to the invention,which has socket-projection fixing devices with a passive reinforcementand socket-projection fixing devices with an active reinforcement, anoptimum balance may be achieved between structural efficiency and thespeed of installation and fixing. If only socket-projection fixingdevices with passive reinforcement are used, the installation can bemade very quickly by assembling succeeding sections without waiting forthe curable material to set. However, safety during the installation isthen relatively low, as is the structural efficiency in the finalsituation. If only socket-projection fixing devices with activereinforcement are used, the installation may be made relatively safer byanchoring at least some of the reinforcements as the sections areassembled, and the structural efficiency in the final situation will behigh once all the tightening means are finally tightened. However, thespeed of installation is relatively slow and the space required to housethe active reinforcement is relatively large. By combiningsocket-projection fixing devices with passive reinforcement and withactive reinforcement in the same horizontal wet joint, the installationof the corresponding tightening means for anchorage in the correspondingholes provides, with minimum tightening torque, a provisional fasteningof the sections immediately after installing one tower section on theother, which secures the joint until the process of filling with curablematerial is completed. Once said curable material reaches its specifiedstrength, stretching of the active reinforcements may commence. It isimportant to provide a fast, efficient method for provisionally securingthe joint, thereby allowing the subsequent installation of severalsections with a high degree of security and enabling the work of fillingwith curable material to a later phase and preventing the work ofinstalling sections from slowing down, which could involve lifting meansincurring high costs.

It is known that in the rings of horizontal wet joints betweenprefabricated sections with a concrete base for the erection of windturbine towers, sealing profiles can be arranged to contain the curablematerial intended to seal the joint. These sealing profiles are normallytwo essentially circumferential profiles arranged concentrically on theupper edge of the lower section of the joint, one of which is arrangedin the vicinity of the inner facing of the sections of the joint and theother of which is arranged in the vicinity of the outer facing of thesections of the joint.

The socket-projection fixing assembly according to the invention mayinclude a translucent sealing profile which allows visual inspection ofthe feed of the curable material during the process of filling thejoint, facilitating inspection and monitoring of the filling operation.Alternatively, the socket-projection fixing assembly according to theinvention may include a thixotropic (highly viscous) curable materialwhich does not require sealing profiles.

Whether it has a sealing profile of one type or the other, or whether ithas no sealing profile, the socket-projection fixing assembly accordingto the invention may include sectorisation means for the ring, i.e.means which form separate compartments along the perimeter of the ringand which enclose one or more socket-projection fixing devices of thesocket-projection fixing assembly according to the invention, in orderto allow separate phases of filling of the ring and hence greatercontrol of the filling operation. Said sectorisation means may beprofiles similar to said sealing profiles arranged simply in the radialdirection instead of in the circumferential direction.

The invention also relates to a process of installing asocket-projection fixing assembly as previously described, whichincludes the steps of:

a) providing a first cylindrical prefabricated section of concrete for awind turbine tower and a second cylindrical prefabricated section ofconcrete for a turbine tower,

b) installing said first and second cylindrical sections within a mutualcoaxial relationship so that said projecting portions of said internalreinforcements and said corresponding ducts face each other and arealigned with each other,

c) bringing said first and second cylindrical sections closer togetherso that said projecting portions of said internal reinforcements arehoused in said corresponding ducts until said first and secondcylindrical sections are adjacent to each other,

d) applying said tightening means to the active reinforcement(s) of saidsocket-projection fixing assembly,

e) applying curable material to the passive reinforcement(s) of saidsocket-projection fixing assembly,

f) stretching the active reinforcement(s) of said socket-projectionfixing assembly by tightening said tightening means;

wherein in addition, in step f, the active reinforcement(s) of saidsocket-projection fixing assembly are stretched by tightening saidtightening means so that said horizontal wet joint is subjected to apartial pre-tensioning, i.e. the active reinforcement(s) of saidsocket-projection fixing assembly are stretched so that they exert aforce which pre-compresses said horizontal wet joint so as to preventthe decompression of said horizontal wet joint for applied loads lowerthan a predetermined load threshold which is in turn lower than themaximum operating load and, from said load threshold, i.e. for appliedloads higher than said load threshold and up to said maximum operatingload, the passive reinforcement(s) of said socket-projection fixingassembly interact in the resistant function by absorbing the tensions towhich the joint may be subjected.

Said procedure for installing a socket-projection fixing assemblyaccording to the invention also includes the application of a curablematerial to the ring formed between said first and second cylindricalsections, preferably in step d).

Moreover, in said procedure for the installation of a socket-projectionfixing assembly according to the invention, in step c), a protectivecover is optionally used for the distal end of at least onereinforcement, in the shape of a cone, which also enables saidprotective cover to act as a guiding mechanism and as a mechanism ofseparation between the reinforcement and the duct of said female parts,preferably in the form of a sheath.

It must be noted that throughout this document the term “distal” isintended to indicate a position that is relatively further from thepoint at which the embedded portion and the projecting portion of thecorresponding reinforcement coincide, and the term “proximal” isintended to indicate a position relatively closer to the point at whichthe embedded portion and the projecting portion of the correspondingreinforcement coincide.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics and advantages of the invention willbecome clear from the following description of an embodiment of theinvention, given solely by way of non-limiting example, with referenceto the accompanying drawings, in which:

FIG. 1 shows an elevation of a wind turbine tower which includes ahorizontal wet joint provided with a socket-projection fixing assemblyaccording to the invention;

FIG. 2 shows a cross-sectional view along line A in FIG. 1 incorrespondence with said horizontal wet joint provided with asocket-projection fixing assembly according to the invention;

FIG. 3 shows a longitudinal cross-section along line I-I in FIG. 2representing a socket-projection fixing device with a passive internalreinforcement, and a longitudinal cross-section along line II-II in FIG.2 representing a socket-projection fixing device with an active internalreinforcement;

FIG. 4 shows a longitudinal cross-section I′-I′ of a socket-projectionfixing device with a passive internal reinforcement as an alternative toa socket-projection fixing device with a passive internal reinforcementas shown in FIG. 3, cross-section I-I, and a longitudinal cross-sectionII′-II′ of a socket-projection fixing device with an active internalreinforcement as an alternative to the socket-projection fixing devicewith an active internal reinforcement shown in FIG. 3, cross-sectionII-II;

FIG. 5 shows a longitudinal cross-section of an assembly of asocket-projection fixing device with a passive internal reinforcementand a socket-projection fixing device with an active internalreinforcement as an alternative to the socket-projection fixing devicesshown in FIG. 3; and

FIG. 6 shows a longitudinal cross-section of an additional assembly of asocket-projection fixing device with a passive internal reinforcementand socket-projection fixing device with an active internalreinforcement as an alternative to the socket-projection fixing devicesshown in FIG. 3.

DETAILED EXPLANATION OF THE INVENTION

In the figures the same or similar parts are denoted by the samereference numeral.

FIG. 1 shows a wind turbine tower 1 which has four successivecylindrical concrete prefabricated sections 2, 2′, 2″, 2′″. A respectivehorizontal wet joint 3, 3′, 3″ is formed between each couple ofsuccessive sections, which joint comprises a respectivesocket-projection fixing assembly according to the invention, i.e. saidtower includes three horizontal wet joints 3, 3′, 3″ and threesocket-projection fixing assemblies according to the invention (saidsocket-projection fixing assemblies according to the invention not shownin FIG. 1).

FIG. 2 shows a cross-sectional view of said tower 1 in correspondencewith the lower horizontal wet joint 3 between a lower section 2 and anupper section 2′, to illustrate the respective socket-projection fixingassembly according to the invention and lower section 2. Saidsocket-projection fixing assembly according to the invention of saidlower horizontal wet joint 3 comprises, in this specific example, thirtysix socket-projection fixing devices with a passive internalreinforcement 7 (only one of which is referenced in FIG. 2 for the sakeof clarity) and twelve socket-projection fixing devices with an activeinternal reinforcement 8 (only one of which is referenced in FIG. 2 forthe sake of clarity). Said lower section 2 is formed by four voussoirs5, which means that the number of devices with an active reinforcement 8is at the same time a multiple of the number of voussoirs 5 in lowersection 2 and the divisor of the total number of devices. The number ofdevices with an active reinforcement 8 is also a multiple of the numberof voussoirs 6 in upper section 2′, upper section 2′ being formed forthis purpose by 1, 2, 3, 4, 6 or 12 voussoirs 6.

FIG. 3 shows a longitudinal section of tower 1 which illustrates saiddevice with a passive reinforcement (cross-section I-I) and alongitudinal section of tower 1 which illustrates said device withactive reinforcement 8 (cross-section II-II).

Specifically FIG. 3, cross-section I-I, shows a device with a passivereinforcement 7 for fixing a lower voussoir 5 prefabricated on aconcrete base for the erection of wind turbine towers and an uppervoussoir 6 prefabricated on a concrete base for the erection of windturbine towers.

Said passive reinforcement 7, in the form of a corrugated bar, ispartially embedded in said lower voussoir 5 so that said passivereinforcement 7 has a lower portion actually embedded in said lowervoussoir 5 and an upper portion which projects from said lower voussoir5. Said upper portion of said passive reinforcement 7 is housed in aduct 10 of passive reinforcement made in said upper voussoir 6. One faceof said upper voussoir 6 includes a hole 11 in correspondence with thedistal end of said upper portion of said passive reinforcement 7, saidhole 11 having a curved development until it reaches said duct 10 ofpassive reinforcement in correspondence with said distal end of saidupper portion of said passive reinforcement 7. Said hole 11 enables afilling material to be inserted in the form of mortar 12, which fillssaid hole 11, said duct 10 of passive reinforcement and ring 17 formedbetween said lower voussoir 5 and upper voussoir 6, said passivereinforcement 7 being anchored to said upper voussoir 6.

FIG. 3, cross-section II-II, shows a device with active reinforcement 8for fixing said lower voussoir 5 and said upper voussoir 6.

Said active reinforcement 8, in the form of a bar or bolt with threadedends, is partially embedded in said lower voussoir 5 so that said activereinforcement 8 has a lower portion actually embedded in said lowervoussoir 5 and an upper portion which projects from said lower voussoir5. Said upper portion of said active reinforcement 8 is housed in a duct9 of active reinforcement made in said upper voussoir 6. One face ofsaid upper voussoir 6 includes a hole 11 in correspondence with thethreaded distal end of said upper portion of said active reinforcement8, said hole 11 having a depth such that it extends to said duct 9 ofactive reinforcement in correspondence with said threaded distal end ofsaid upper portion of said active reinforcement 8. Said hole 11 providesaccess to a plurality of tightening means 14, 16 applied to saidthreaded distal end of said upper portion of said active reinforcement 8against one face supporting face 15 of said hole 11. Said tighteningmeans comprise a nut 14 and a plate 16, said nut 14 being threaded ontosaid threaded distal end of said upper portion of said activereinforcement 8 and said plate 16 being inserted between said nut 14 andsaid supporting face 15, said plate 16 also having a plurality of drainducts 19 which provide a fluid communication between said duct 9 ofactive reinforcement and said hole 11.

Said device with active reinforcement 8 also comprises a plurality ofanchoring means 4 applied in a fixed manner to the threaded distal endof said lower portion of said active reinforcement 8 and a sheath 13arranged around said lower portion of said active reinforcement 8 sothat said active reinforcement 8 can be expanded or shrunk inside saidsheath 13 and inside said active reinforcement duct 9 by the actuationof said nut 14 for stretching said active reinforcement 8.

Said hole 11 also enables a filling material to be inserted in the formof mortar 12, which fills said hole 11, said active reinforcement duct 9and ring 17 formed between said lower voussoir 5 and upper voussoir 6.

As can be seen in FIG. 3, both in cross-section I-I and in cross-sectionII-II, the horizontal wet joint 3 includes two sealing profiles 20 whichdelimit said ring 17 and contain said mortar 12.

In the embodiment shown in FIGS. 1, 2 and 3, the following parametersmay be used specifically:

-   -   4 voussoirs in lower section 2    -   4 voussoirs in upper section 2′    -   12 positions of active reinforcement 8    -   36 positions of passive reinforcement 7    -   Diameter of lower joint 3: 7 m    -   The joint is dimensioned to be able to withstand with a        sufficient degree of safety a maximum design torque not        exceeding 60000 KNm:    -   The partial pre-tension of the joint, together with the inherent        weight of tower 1 and the wind turbine in its head, provides a        compressive force in the joint which presents it from        decompressing at torques below 25000 KNm.    -   Thus the aim is the joint to remain compressed at all times        under normal or fatigue loads. Under unusually high or extreme        loads the joint may be subjected to tensions which passive        reinforcements 7 are designed to resist.

FIG. 4 shows a longitudinal section I′-I′ of a socket-projection fixingdevice with passive internal reinforcement 7 as an alternative to thedevice in FIG. 3, cross-section I-I, and a longitudinal section II′-II′of a socket-projection fixing device with active internal reinforcement8 as an alternative to the device in FIG. 3, cross-section II-II.

Specifically FIG. 4, section I′-I′, shows a device with passivereinforcement 7 for fixing a lower voussoir 5 prefabricated on aconcrete base for the erection of wind turbine towers and an uppervoussoir 6 prefabricated on a concrete base for the erection of windturbine towers.

Said passive reinforcement 7, in the form of a corrugated bar, ispartially embedded in said upper voussoir 6 so that said passivereinforcement 7 has an upper portion actually embedded in said uppervoussoir 6 and a lower portion which projects from said upper voussoir6. Said lower portion of said passive reinforcement 7 is housed in apassive reinforcement duct 10 made in said lower voussoir 5. The upperedge of said lower voussoir 5 includes a hole 11 in correspondence withthe proximal end of said lower portion of said passive reinforcement 7,said hole 11 having an inclined development until it reaches laterallysaid passive reinforcement duct 10 in correspondence with said proximalend of said lower portion of said passive reinforcement 7. Said hole 11facilitates the insertion of a filling material in the form of mortar12, which fills said hole 11, said passive reinforcement duct 10 andring 17 formed between said lower voussoir 5 and voussoir 6, saidpassive reinforcement 7 being anchored to said lower voussoir 5. Thedistal end of said passive reinforcement duct 10 has a drain duct 19which provides a fluid communication between said passive reinforcementduct 10 and the surrounding area. The purpose of said drain duct 19 atthe basis of said passive reinforcement duct 10 is to allow the completedrainage of water from said passive reinforcement duct 10 before fillingwith mortar. It will generally be plugged before proceeding with fillingwith said mortar 12.

FIG. 4, section II′-II′, shows a device with active reinforcement 8 forfixing said lower voussoir 5 and said upper voussoir 6.

Said active reinforcement 8, in the form of a pre-tensioning cable, ispartially embedded in said upper voussoir 6 so that said activereinforcement 8 has an upper portion actually embedded in upper voussoir6 and a lower portion which projects from said upper voussoir 6. Saidlower portion of said active reinforcement 8 is housed in an activereinforcement duct 9 made in said lower voussoir 5. One face of saidlower voussoir 5 includes a hole 11 in correspondence with the distalend of said lower portion of said active reinforcement 8, said hole 11having a depth such that it extends to said active reinforcement duct 9in correspondence with said distal end of said lower portion of saidactive reinforcement 8. Said hole 11 provides access to a plurality oftightening means applied to said distal end of said lower portion ofsaid active reinforcement 8 against one supporting face of said hole 11.Said tightening means are similar to tightening means 14, 16 of thedevice shown in FIG. 3, cross-section II-II, and consist of an anchorplate and a clamp with a key for anchoring the cable.

Said hole 11 also enables to inject a filling material in the form ofmortar 12, which fills said hole 11. Optionally active reinforcementduct 9 and ring 17 formed between said lower voussoir and upper voussoir6 may also be filled with mortar from said hole 11. Said mortar 12 mayalso be intruded through a separate ring 17.

As can be seen from FIG. 5, both in section I′-I′ and section II′-II′,the horizontal wet joint represented may have a radially inclineddevelopment and includes a sealing profile 20 which delimits said ring17 close to the lowest end of said development so as to contain suchmortar 12.

FIG. 5 shows a longitudinal section of an assembly of thesocket-projection fixing device with passive internal reinforcement andthe socket-projection fixing device with active internal reinforcementas an alternative to the socket-projection fixing devices shown in FIG.3.

Specifically FIG. 5 shows a device with two passive reinforcements 7, 7′and an active reinforcement 8 for fixing a lower voussoir 5prefabricated on a concrete base for the erection of wind turbine towersand an upper voussoir 6 prefabricated on a concrete base for theerection of wind turbine towers.

One of said passive reinforcements 7, in the form of a fork, ispartially embedded in said lower voussoir 5 so that said passivereinforcement 7 has a lower portion actually embedded in said lowervoussoir 5 and an upper portion which projects from said lower voussoir5. Said upper portion of said passive reinforcement 7 is housed in aduct which is in this case in the form of cavity 10 made in said uppervoussoir 6. Another of said passive reinforcements 7′, in the form of afork, is partially embedded in said lower voussoir 6 so that saidpassive reinforcement 7′ has an upper portion actually embedded in saidupper voussoir 6 and a lower portion which projects from said uppervoussoir 6. Said lower portion of said passive reinforcement 7′ ishoused in a duct which is in this case in the form of cavity 10′ made insaid lower voussoir 5. Said passive reinforcements 7, 7′ are juxtaposedlaterally and said cavities 10, 10′ are located symmetrically relativeto the plane of the horizontal wet joint shown.

A filling material, in the form of mortar 12, fills said cavities 10,10′, said passive reinforcements 7, 7′ being anchored to both lowervoussoir 5 and upper voussoir 6. Said passive reinforcements, 7, 7′ alsoinclude four rods 23 located horizontally against the trough of saidpassive reinforcements 7, 7′ to improve the anchoring of said passivereinforcements 7, 7′ to mortar 12.

Said active reinforcement 8, in the form of a pre-tensioning cable, ispartially embedded in said upper voussoir 6 so that said activereinforcement 8 has an upper portion actually embedded in said uppervoussoir 6 and a lower portion which projects from said upper voussoir6. Said lower portion of said active reinforcement 8 is housed in aactive reinforcement duct 9 made in said lower voussoir 5 incorrespondence with said cavity 10′. One face of said lower voussoir 5includes a hole 11 in correspondence with the threaded distal end ofsaid lower portion of said active reinforcement 8, said hole 11 having adepth such that it extends to said active reinforcement duct 9 incorrespondence with said distal end of said lower portion of said activereinforcement 8. Said hole 11 provides access to a plurality oftightening means applied to said threaded distal end of said lowerportion of said active reinforcement 8 against a support face of saidhole 11. Said tightening means are similar to means 14, 16 for anchoringthe device shown in FIG. 3, cross-section II-II, and consist of ananchor plate and a clamp with key for anchoring the cable

Since said active reinforcement duct 9 is made in said lower voussoir 5in correspondence with said cavity 10′, said mortar 12 also fills saidactive reinforcement duct 9. It must be noted that said activereinforcement 8 is sheathed so that it does not adhere to mortar 12 andcan be subsequently tightened after said mortar 12 has set

The horizontal wet joint shown also includes a sealing profile 20 whichdelimits said ring 17 at the radial end of said ring 17 opposing saidcavities 10, 10′.

FIG. 6 shows a longitudinal section of an additional assembly of thesocket-projection fixing device with passive internal reinforcement andthe socket-projection fixing device with active internal reinforcementas an alternative to the socket-projection fixing devices in FIG. 3.

Specifically, FIG. 6 shows a device with two passive reinforcements 7,7′ and an active reinforcement 8 for fixing a lower voussoir 5prefabricated on a concrete base for the erection of wind turbine towersand an upper voussoir 6 prefabricated on a concrete base for theerection of wind turbine towers.

One of said passive reinforcements 7, in the form of a fork, ispartially embedded in said lower voussoir 5 so that said passivereinforcement 7 has a lower portion actually embedded in said lowervoussoir 5 and an upper portion which projects from said lower voussoir5. Said upper portion of said passive reinforcement 7 is housed in apassive reinforcement duct 10 made in said upper voussoir 6. Another ofsaid passive reinforcements 7′, in the form of a fork, is partiallyembedded in said upper voussoir 6 so that said passive reinforcement 7′has an upper portion actually embedded in said upper voussoir 6 and alower portion which projects from said upper voussoir 6. Said lowerportion of said passive reinforcement 7′ is housed in a passivereinforcement duct 10′ made in said lower voussoir 5. Said passivereinforcements 7, 7′ are juxtaposed laterally and said ducts 10, 10′ arelocated symmetrically in relation to the plane of the horizontal wetjoint shown.

Said active reinforcement 8, in the form of a bar or bolt with threadedends, is partially embedded in said lower voussoir 5 so that said activereinforcement 8 has a lower portion actually embedded in said lowervoussoir 5 and an upper portion which projects from said lower voussoir5. Said upper portion of said active reinforcement 8 is housed in anactive reinforcement duct 9 made in said upper voussoir 6 incorrespondence with said ducts 10, 10′. One face of said upper voussoir6 includes a hole 11 in correspondence with the threaded distal end ofsaid upper portion of said active reinforcement 8, said hole 11 having adepth such that it extends to said active reinforcement duct 9 incorrespondence with said threaded distal end of said upper portion ofsaid active reinforcement 8. Said hole 11 provides access to a pluralityof tightening means 14, 16 applied to said threaded distal end of saidupper portion of said active reinforcement 8 against a supporting face15 of said hole 11. Said tightening means are similar to means 14, 16for tightening the device in FIG. 3, cross-section II-II, and consist ofan anchor plate and a clamp with a key for anchoring the cable.

Said device with active reinforcement 8 also comprises a plurality ofanchoring means 4 applied in a fixed manner to the threaded distal endof said lower portion of said active reinforcement 8 and a sheath 13arranged around said lower portion of said active reinforcement 8 sothat said active reinforcement 8 can be expanded or shrunk inside saidsheath 13 and inside said active reinforcement duct 9 by actuating saidnut 14 for tightening said active reinforcement 8.

Said hole 11 also allows the introduction of a filling material in theform of mortar 12 which, since said active reinforcement duct 9 is madein said upper voussoir 6 in correspondence with said ducts 10, 10′, itfills said hole 11, said active reinforcement duct 9, said ducts 10, 10′and ring 17 formed between said lower voussoir 5 and upper voussoir 6,said active reinforcement 8 being anchored to said upper voussoir 6 alsoby said mortar 12 and said passive reinforcements 7, 7′ being anchoredto both lower voussoir 5 and upper voussoir 6. It must be noted thatsaid active reinforcement 8 is sheathed so that it does not adhere tomortar 12 and can be tightened later when said mortar 12 has set.

As can be seen in FIG. 6, the horizontal wet joint shown includes twosealing profiles 20 which delimit said ring 17, which profiles containsaid mortar 12.

Obviously, the principle of the invention remaining the same, theembodiments and design details may widely vary from those described andillustrated purely by way of non-limiting example, without therebydeparting from the scope of the invention as defined in the attachedclaims.

Specifically, by way of non-limiting illustration, devices with anactive reinforcement and devices with a passive reinforcement of anytype may be used in the same horizontal wet joint, combining themwhether they are of the same type or of a different type.

1. An internally reinforced, socket-projection fixing assembly for ahorizontal wet joint formed between two cylindrical prefabricatedconcrete sections, for a wind turbine tower, which assembly comprises atleast one socket-projection fixing device with active internalreinforcement and at least one socket-projection fixing device withpassive internal reinforcement, so that said active internalreinforcement and said passive internal reinforcement each include anembedded portion which is embedded in a first section of saidcylindrical sections, and a projecting portion which projects from saidfirst section and is housed in a duct in a second section of saidcylindrical sections, wherein said active internal reinforcementincludes tightening means which are arranged in said projecting portionof said active internal reinforcement and against a supporting surfaceof one of said cylindrical sections so that said active internalreinforcement is anchored to said supporting surface and is tightened bymeans of said tightening means, and said passive internal reinforcementincludes cured material which is arranged at least partially around saidprojecting portion of said passive internal reinforcement and adheres tothe inside of passive reinforcement duct in which is arranged saidprojecting portion of said passive internal reinforcement.
 2. Thesocket-projection fixing assembly according to claim 1, wherein at leastone of said first and second sections is formed by voussoirs.
 3. Thesocket-projection fixing assembly according to claim 1, wherein saidcylindrical sections comprise voussoirs and said socket-projectionfixing assembly comprises a number of socket-projection fixing deviceswith active internal reinforcement, which is at the same time a multipleof the number of voussoirs in the first section, a multiple of thenumber of voussoirs in the second section and the divisor of the totalnumber of socket-projection fixing devices with active reinforcement (8)and with passive reinforcement.
 4. The socket-projection fixing assemblyaccording to claim 1, wherein said tightening means has a nut which isthreaded onto a threaded end of said active internal reinforcement andwhich is tightened against said supporting surface.
 5. Thesocket-projection fixing assembly according to claim 4, wherein said nutis tightened against said supporting surface with the insertion of ananchor plate and/or a curable material.
 6. The socket-projection fixingassembly according to claim 4, wherein said nut is tightened againstsaid supporting surface with the insertion of an anchor plate, saidsecond section is arranged above said first section, and said anchorplate comprises at least one bore which acts as a drain pipe for the airoutlet.
 7. The socket-projection fixing assembly according to claim 1,wherein said passive reinforcement duct includes a sheath which receivessaid projecting portion of said passive internal reinforcement and saidpassive reinforcement duct 40) is filled with curable material.
 8. Thesocket-projection fixing assembly according to claim 1, wherein saidsecond section has a working facing which includes at least one hole incorrespondence with the distal end of a projecting portion of an activeinternal reinforcement, said hole having a depth such that it at leastextends to the respective active internal reinforcement duct incorrespondence with said distal end of said projecting portion of saidactive internal reinforcement and having such dimensions that theyenable the respective tightening means to be housed in the interior ofsaid hole.
 9. The socket-projection fixing assembly according to claim8, wherein the respective supporting surface is located on the innerwall of said hole.
 10. The socket-projection fixing assembly accordingto claim 1, wherein said second section is arranged above said firstsection and said second section has a working facing which includes atleast one hole in correspondence with the distal end of a projectingportion of a passive internal reinforcement (7), said hole having adepth such that it at least extends to the respective passivereinforcement duct in correspondence with said distal end of saidprojecting portion of said passive internal reinforcement, and saidsheath having an extension which extends along said hole until itreaches at least the inlet of said hole.
 11. The socket-projectionfixing assembly according to claim 8, wherein said hole is not opened bythe facing opposing the working facing.
 12. The socket-projection fixingassembly according to claim 8, wherein said working facing is the facingorientated towards the inner space enclosed by said second section. 13.A method of installing a socket-projection fixing assembly according toclaim 1, the method comprising the steps of: a) providing a firstcylindrical prefabricated section of concrete for a wind turbine towerand a second cylindrical prefabricated concrete section for a turbinetower, b) installing said first and second cylindrical sections within amutual coaxial relationship so that said projecting portions of saidinternal reinforcements and said corresponding ducts face each other andare aligned with each other, c) bringing said first and secondcylindrical sections closer together so that said projecting portions ofsaid internal reinforcements are housed in said corresponding ductsuntil said first and second cylindrical sections are adjacent to eachother, d) applying said tightening means to the active reinforcement, e)applying curable material to the passive reinforcement(s), f) stretchingthe active reinforcement(s) by tightening said tightening means; whereinin step f) said active reinforcement(s) are tightened by tightening saidtightening means so that said horizontal wet joint is subjected to apartial pre-tensioning.
 14. The method of installing according to claim13, further comprising application of a curable material to ring formedbetween said first and second cylindrical sections.
 15. The method ofinstalling according to claim 13, wherein said step d) also includes theapplication of curable material to ring formed between said first andsecond cylindrical sections.
 16. The method of installing according toclaim 13, wherein said step c) also includes the use of a protectivecover for the distal end of at least one reinforcement.
 17. The methodof installing according to claim 16, wherein said protective cover isconical in shape.